Twin inglenook chimney pots... draw

[dinglem]

Hi all,

As detailed in another thread a while back you may know that i have recently opened up my original inglenook; it has cleaned up very nicely and i am now considering the practicalities of having an open fire. It is very large and standing in the fireplace itself and looking up, you can clearly see that at the top of the stack (i.e. above the roofline) the chimney splits into two; the vertical column leading up to the top of the chimney above the roofline being split by a single layer of bricks with a 'V' shaped dividing piece at the very bottom. There is room on top of the chimney for a pair of pots, but currently there is only one. The second is capped and sealed for some reason??

I am assuming that if i open up the second vent and add a pot to this then the overall draw will be improved? Is this correct?

I will obviously therefore be changing both pots so i have a matching pair. Would fitting taller pots at this time serve to improve the draw even more???

Does anybody else have something similar? I am wondering why the second pot was removed and capped in the first place??? Thoughts?

The second chimney stack at the other end of my house has two pots (front room and bedroom fireplaces sharing this chimney) so two pairs of pots will actually prove easier on the eye...

Cheers Martin.

 

[worms]

I'm not sure I ever really understood the description of your chimney when you posted before, but can you confirm that there were two distinct flues into the inglenook and that it is just one of these that then splits at the top? If so, where did the other one go?

Is it possible that the chimney didn't originally have pots at all and that what you are seeing from below is just a means of cross-bracing the inside of the chimney head?

 

[dinglem]

Sorry for the confusion. It's just one large inglenook fireplace (2.8m wide and 1.25m deep) that when looking upwards dramatically reduces in size through the house moving up, and then when it gets to the roofline and above it splits into two, with one side being closed off.

Yes, you could be correct regarding it originally having no pots at all and also that what i am seeing is cross-bracing. I hadn't thought of that until you mentioned it. I am now wondering what the effects of having both sides of this 'cross-bracing' or whatever it may be open will have on the draw, and also whether taller pots will have any impact?

(FYI - where i am currently working the use of photobucket is prohibited and as such i cannot add any photo's to the old thread to show the fully exposed inglenook).

 

[worms]

Sorry, it was your previous post that confused me:

what i would describe as 2 columns that run up the chimney either side of where i assume the fire should go (central). These columns can be followed up the chimney and seem to be to channel smoke up and across to the centre line of the house where the chimney exit is located. What is odd is that the one on the left curves out over the fire and then back on itself,

I had interpreted this as there being a division all the way from the bottom and that one side was then splitting again at the top.

The picture looks like the split is lower down than the chimney head, so perhaps my first suggestion would not work. Someone else might be able to copy your original pictures across to this thread, I couldn't get it to work. The original thread is here

 

[Herbs]

I currently have what you are after in one of my inglenooks and have been advised to get one of the pots capped as soon as I get a chance. There is only meant to be one exit (pot) per fireplace otherwise it can cause issues with down draughts and potential chimney fires - I don't understand the ins and outs of it but it would be worth getting someone professional in before you make any changes.

 

[robgil]

Is that somewhere to smoke/cure meat?

 

[worms]

Is that somewhere to smoke/cure meat?

If you have a look at the original thread, you can see that the dead leg in question looks to be too high up to have been used for smoking, I suppose it might be as Herbs suggests and has been closed off more recently on grounds of safety. But it has been quite a sophisticated fire set-up in its day, so who knows!

 

[Schoolmarm]

Is there any chance that the capped one was originally a fireplace in the bedroom that has lost the base for whatever reason?

 

[dinglem]

I don't think there was ever a fireplace upstairs in the bedroom, as all there is up there is a huge and very uneven chimney breast which slopes away dramatically from floor to ceiling as the chimney itself reduces in width/depth. There is also no evidence of brickwork having been removed.

I think what i'm going to do first is light a fire in the inglenook and warm it up/dry it out. It hasn't been opened up for very long and i'm guessing is still airing out, and i haven't had a good fire going in there yet. Once i have seen what the draw is actually like i can make a decision on which way to go. I was really interested in what difference opening up the second pot might have made and also whether increasing pot height can make significant differences also. Good to hear that others have experiences with twin pots, albeit not very good ones! :?

Many thanks for the input!

 

[Penners]

I am assuming that if i open up the second vent and add a pot to this then the overall draw will be improved? Is this correct?

I have no particular expertise on this subject (or any other!) but I'm not sure that your assumption is a given. It may be - or it may not.

My scant understanding is that a well-designed chimney works on a venturi effect - that is, the movement of wind across the "mouth" of the chimney pot creates a partial vacuum inside the stack. This helps the combustion products to be drawn up the chimney (in addition to the rising effect already created by the warmth of the gases).

My befuddled brain tells me that if you increase the volume of the chimney (which - by opening up the other flue - you are effectively doing) then you will reduce the speed of the air movement within it. So I'm not certain whether the addition of an extra escape route will increase or reduce the draw.

Others may bring a much more knowledgeable point-of-view to this, but in the absence of genuinely expert opinion, my approach would be a suck-it-and-see one. Have you actually tried lighting a fire in the inglenook, with the one flue in operation? If not, then this is where I would start. If the fireplace hasn't been used for a long time, don't make a snap judgement if it initially starts to smoke. Give it a bit of time, get a good fire going and allow the chimney to warm up. Only then will you really know whether it works properly as it is.

If it does work, then the old adage becomes appropriate: "If it ain't broke, don't fix it"!

If it won't draw properly, then you have the option of opening up the second flue to see what effect this has.

By the way, you say that you will remove the existing pot in order to fit a matched pair. Personally, I wouldn't. Chimney pots are expensive, and many houses have unmatched pairs of them. For me, it's part of the history and character of the house.

 

[dinglem]

Penners, thank you for your advice. Wise words as usual.

I agree that i should probably get the fire going first and try it out. I have a fire basket in place so i'll give that a go and get the chimney nice and hot; if the draw is good then no changes necessary.

The only reason i was looking at a matching pair of pots was that in my head i was assuming that double the openings would assist the draw, which judging by the comments made here may not necessarily be the case. With that in mind if i was up there adding one then i thought i might as well change the exisiting one so the pair matched.

I'll get on to it and report back as soon as i (eventually) return home.

Thanks again!

 

[88v8]

Yes, a taller pot will improve the draw.
Something like this, with upwards louvres, will draw best of all.
http://www.ebay.co.uk/itm/PAIR-VICTORIAN-EDWARDIAN-TALL-CHIMNEY-POTS-/190599707613?pt=UK_Antiques_Architecural_RL&hash=item2c60a0bbdd
Perhaps not very 'period', and I'm not encouraging you to have two pots but your huge inglenoook will probably smoke like billyo, anything that improves the draw would make it more tolerable.

The room will also need a large air inlet, if you want it to draw at all well.

Ivor

 

[Penners]

The room will also need a large air inlet, if you want it to draw at all well.

Yes, that's true. The amount of air going up the chimney will need to be balanced by the amount of air entering the room. But I wouldn;t be in too much of a hurry to start cutting holes in anything. Quite often, the incoming air finds plenty of space under doors, around windows, etc.!

Once you've got your fireplace working, let's discuss your problem with draughts!

 

[dinglem]

Thanks for the great information people, and thanks for taking the time to post that link to the pots on auction currently.

I'd assumed that taller pots might give improved draw but it's still good to hear.

 

[Flyfisher]

I'm not entirely convinced that a taller pot will increase the draw significantly. How much taller are we talking about? An extra foot on a, say, 35 foot chimney? Such a thing may help with 'blowback' though, if the chimney height is close to nearby obstructions such as trees, other roofs etc.

In a previous house, we had success with an 'H-pot', which was a terracotta thing that was simply slotted into the existing pot. No need to change anything and completely reversible if it doesn't work.

My understanding is H-pots work by increasing the surface area over which the wind blows, thus increasing the venturi that Penners mentioned. Whatever the actual mechanism, it worked for us, though my limited experience of such things would suggest that chimneys are all individual things, with their own particular quirks, and it takes a while to get to know them and how to get the best out of them.

An H pot insert:

A complete H pot:

 

[Penners]

I'd assumed that taller pots might give improved draw

That's the trouble with chimneys - as FF says, you just can't make assumptions! There are various principles that you can apply to them, but you never really know whether a solution is going to work until you've actually tried it.

 

[88v8]

H pots also have the merit of keeping the rain out, and birds are less likely to find their way down them.

Ivor